Cerebral palsy

by Mai Tran

Cerebral palsy (CP), or static encephalopathy, is the name for a collection of movement disorders caused by brain damage that occurs before, during, or shortly after birth. A person with CP is often also affected by other conditions caused by brain damage.

The affected muscles of a person with CP may become rigid or excessively loose. The person may lose control of muscles, or have problems with balance and coordination. A combination of these is also possible. Those with CP may be primarily affected in the legs (paraplegia or diplegia), or in the arm and leg of one side of the body (hemiplegia), or all four limbs may be involved (quadriplegia).

A person with CP may also be affected by a number of other problems, including seizure disorder, visual deficits, hearing problems, mental retardation, learning disabilities, and attention deficit hyperactivity disorder . None of these is necessarily part of CP, however, they may accompany the disorder.

CP affects approximately 500,000 children and adults in the United States, and is diagnosed in more than 6,000 newborns and young children each year. It is not an inherited disorder, and as of yet there is no way to predict with certainty which children will develop CP. It is not a disease, and is not communicable. CP is a nonprogressive disorder, which means that symptoms neither worsen nor improve over time. However manifestation of the symptoms may become more severe over time. For example, rigidity of muscles can lead to contractures and deformities that require a variety of interventions.

Cerebral palsy is caused by damage to the motor control centers of the brain. When the nerve cells (neurons) in these regions die, the appropriate signals can no longer be sent to the muscles under their control. The resulting poor control of these muscles causes the symptoms of CP.

The brain damage leading to CP may be caused by lack of oxygen (asphyxia), infection, trauma, malnutrition, drugs or other chemicals, or hemorrhage. In most cases it is impossible to determine the actual cause, although premature birth is recognized as a significant risk factor. It was once thought that difficult or prolonged delivery was responsible for many cases of CP, but most researchers now believe that the great majority of cases result from brain damage occurring before birth. The same injury that damages the motor areas can harm other areas as well, leading to other problems commonly associated with CP.

If brain cells do not get enough oxygen because of poor circulation, they may die. Defects in circulation in the developing brain may cause CP in some cases. Asphyxia during birth is also possible, and about half of newborns known to have suffered asphyxia during birth (perinatal asphyxia) develop CP. However, asphyxia during birth is usually considered a symptom of an underlying neurological problem in a newborn, rather than its cause, and the resulting CP may be another sign of that problem. Asphyxia after birth can be caused by choking, poisoning (such as from carbon monoxide or barbiturates), or near-drowning.

The fetal brain may be damaged by an infection contracted by the mother. Infections correlated with CP include rubella (German measles), toxoplasmosis (often contracted from cat feces), cytomegalovirus (a herpes virus), and HIV (the virus that causes AIDS). Encephalitis and meningitis, infections of the brain and its coverings, can also cause CP when contracted by infants.

Physical trauma to the pregnant mother or infant may cause brain damage. Blows to the infant's head, as from a motor vehicle accident, violent shaking, or other physical abuse can damage the infant's brain. Maternal malnutrition may cause brain damage, as can the use of drugs, including cocaine or alcohol. Although these factors may cause CP, they may be more likely to cause mental retardation or other impairments.

Incompatibility between the Rh blood types of mother and child was once a major cause of athetoid CP, one type of movement impairment seen in cerebral palsy. In some cases, this incompatibility can cause the mother's defense (immune) system to attack and destroy the child's blood cells during pregnancy, a condition called erythroblastosis fetalis. High levels of a blood cell breakdown product called bilirubin in a child's circulation, leading to yellowish pigmentation of the skin caused by bile (jaundice) can result in brain damage. This condition is now rare because of testing procedures that identify potential Rh incompatibility, and treatment that prevents the mother's immune system from attacking the child's blood cells. Jaundice that does occur can be treated with special lights that help the breakdown of bilirubin. Blood transfusions for the child are also possible in extreme cases. Despite the virtual elimination of this cause of CP in the last few decades, CP rates have not declined, largely because of the increase of survival of premature babies.

Prematurity is one of the most significant risk factors for CP. About 7% of babies weighing less than three pounds at birth develop CP, and the risk increases dramatically as weight falls. Prematurity may increase the risk of CP because of the increased likelihood of hemorrhaging in the brain associated with low birth weight. Brain hemorrhage is most common in babies weighing less than four pounds at birth, and the risk increases as weight decreases. The hemorrhage may destroy brain tissue, either through asphyxia or release of toxic breakdown products.

The symptoms of CP are usually not noticeable at birth. As children develop through the first 18 months of life, however, they progress through a predictable set of developmental milestones. Children with CP will develop these skills more slowly because of their motor impairments, and delay in reaching milestones is usually the first symptom of CP. The more severe the CP, the earlier the diagnosis is usually made.

Selected developmental milestones, and the ages at which a child will normally acquire them, are given below. There is some cause for concern if the child does not acquire the skill by the age shown in parentheses:

• sits well unsupported, 6 months (8-10 months)
• babbles,6 months (8 months)
• crawls, 9 months (12 months)
• finger feeds, holds bottle, 9 months (12 months)
• walks alone, 12 months (15-18 months)
• uses one or two words other than dada/mama, 12 months (15 months)
• walks up and down steps, 24 months (24-36 months)
• turns pages in books, removes shoes and socks, 24 months (30 months)

Children do not consistently favor one hand over the other before 18 months, and doing so may be a sign that the child has difficulty using the other hand. This same preference for one side of the body may show up as an asymmetric crawling effort, or continuing to use only one leg for the work of stair climbing after age three.

It must be remembered that children normally progress at somewhat different rates, and slow initial accomplishment is often followed by normal development. There are also other causes for delay in reaching some milestones, including problems with vision or hearing. Because CP is a non-progressive disease, loss of previously acquired milestones indicates that CP is not the cause of the problem.

The impairments of CP become recognizable in early childhood. The type of motor impairment and its location are used as the basis for classification. There are five generally recognized types of impairment:

• Spastic. Muscles are rigid, posture may be abnormal, and fine motor control is impaired.
• Athetoid. It is marked by slow, writhing, involuntary movements.
• Hypotonic. Muscles are floppy, without tone.
• Ataxic. Balance and coordination are impaired.
• Dystonic. Impairment is mixed.

The location of the impairment usually falls into one of three broad categories:

• Hemiplegia. One arm and one leg on the same side of the body are involved
• Diplegia. Both legs; arms may be partially involved.
• Quadriplegia. All four extremities are involved.

A person with CP may be said to have spastic diplegia, or ataxic hemiplegia, for instance. CP is also termed mild, moderate, or severe, although these are subjective categories with no firm boundaries.